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WA4/U R. J. HESS PRESS Filed June 16, 1944 Patented Jan. 20, 1948 UNITEDSTATES PATENT OFFICE PRESS Relza J. Hess, Chicago, Ill., assigner toAmerican Steel Foundries, Chicago, Ill., a corporation Aoi' r New JerseyApplication June 16, 1944, Serial No. 540,608

Claims. 1

between said platens, as will be clearly understood by those skilled inthe art.

My novel press is so constructed that the yieldable platen, after apredetermined period of time, is actuated to close the dies and exertthe necessary pressure thereon to mold the plastic material to its nalform Within the dies. l

Another object of my invention is to provide an arrangement wherein anovel portable hydraulic unit may be inserted into a pre-existingmechanical press for the purpose of adapting said press to the moldingof plastics. I provide novel control means for the press and theportable unit, which control means permit the hydraulically operatedplaten of the unit to yield under a predetermined pressure exerted bythe mechanically actuated press platen which is automatically stopped inits advanced position, said control means being operable, after apredetermined period of time necessary for the breathing and heatingcycle, to direct high pressure actuating fluid into the hydraulic unit,thereby causing its platen to exert the necessary pressure to close thedies between the two platens, whereby the plastic material is molded toits iinal form Within the dies.

The high pressure is maintained within the hydraulic unit for a periodof time necessary to insure solidication of the molded material, andthereafter, my novel control means is operable to by-pass this highpressure. Thereafter, the mechanical platen may be retracted, whereuponthe low hydraulic pressure within the supply system for the unit isoperable to move its platen to advanced position for a new cycle.

In the drawings, the figure illustrates a front elevation of my novelpress with the portable unit shown in section. The hydraulic andelectric circuits utilized in my novel arrangement are diagrammaticallyillustrated in this ligure.

Describing my invention in detail, the press includes a press framegenerally designated 2 and top and bottom platens 4 and 6, the topplaten being actuated in conventional manner by a toggle mechanismconsisting of toggle links 8 and I0 pivoted respectively at I2 and I4 tothe platen 4 and the frame 2. The toggle mechanism is actuated in usualmanner by a crankshaft I6 which drives a connecting rod I8 pivoted at 20to the center joint of the toggle mechanism. The crank shaft I6 isoperated by a motor (not shown) to which it is connected by aconventional air actuated clutch indicated at 2|, said clutch 2| beingoperated by air lines 22 and 24 connected to an air valve 26 which isoperable to direct compressed air from a shop air line (not shown) tosaid pipes 22 and 24, thereby actuating the air clutch 2I to engage anddisengage the crankshaft I6 with respect to the motor as will be clearlyunderstood by those skilled in the art.

The lower platen 6 is part of a novel portable hydraulic unit generallydesignated 21 and shown and described in detail in my co-pendingapplication, Serial No. 492,363, led June 26, 1943, in the United StatesPatent Oilice for Hydraulic safety bed. The platen 6 comprises acylinder 28 Within which is slidably tted a ram 30 mounted on a baseplate or bottom member 32 which also carries guide posts 34, 34 slidablyengaged with the platen 6 as described in detail in said co-pendingapplication. The base plate 32 of the unit 2l is seated on the bed 36 ofthe press frame 2 which thus alfords convenient support for said unit.It will be understood that while the unit 2'I is herein illustrated as aportable device, if desired, the unit may be built into the press by anysuitable construction such as is conventional in the art, and it willalso be understood that in the event that the unit 21 is built into thepress, the upper platen may, if desired, be hydraulically operated byany suitable conventional hydraulic motor means.v

Hydraulic actuating fluid for the unit 21 is conveyed to the cylinder 28through a port 38 in the ram, and a supply line 40 is connected to saidport, said supply line comprising a holding valve 42 including a chamber44 with ports closed by two spring-pressed stems or seat members 46 andk48, the spring pressure on the member 46 being relatively light ascompared with that on the member 48. It may be noted at this point thatthe member 46 is hollow and includes a port 49 in order to afford abalancing of the hydraulic pressures against said member 46, thuspermitting its associated spring to urge it to closed position topositively prevent flow of fluid through the holding valve 42 in thedirection away from the unit 21. Thus the hydraulic fluid within thesystem may only iiow in this direction through the port closed by thevalve member 48 when the pressure within the cylinder 28 exceeds apredetermined maximum depending upon the adjustment of the screw 5|. Thefunction of the holding valve 42 will hereinafter be described in detailin connection with the operation of the press.

The supply line 48 is connected through a solenoid operated by-passvalve 5D to a tank or reser- Voir 52 containing a quantity of hydraulicliquid, such as oil, indicated at 54 and a charge of compressed gas,such as air. The compressed air is admitted to the upper end of thereservoir 52 by the shop air line 56. The reservoir 52 Vis connected atits lower end to the pump line 58 connected to the pump 60 which is'driven by `a motor 62, both the pump and the motor being mounted on asump 64 which collects slippage or `leakage oil vfrom the pump 60 bymeans of a conduit 66 which communicates with the interior of the pumpcasing, as will Vbe clearly understood by those skilled in the art. lThepump 69 pumps oil from the sump 64 through a foot valve 68 and a oatvalve 18 in the pump line 58, said float valve opening whenever theliquid level in the sump reaches a predetermined low level. Thus,slippage or' leakage oil from the pump is recovered and pumped back intothe system. A relief valve 12 is provided for the purpose of preventingthe buildingr up of dangerous pressures by the pump, and this valve maybe set to by-pass the pump into the reservoir 52 at any desired maximumpressure such as, for example, 2500 lbs. per square inch.

In operating my novel device, the operator `pushes the start button 14,thereby closing a circult through the relay 16 and the before-mentionedair valve 26, said circuit being established between the main leads 80and 82 which are connected to any suitable source of electric power (notshown). Energization of the relay 16 closes a holding circuittherethrough and a holding circuit through the air valve 26 across therelay contact points 84 and 86 which are connected by a switch member 81in the usual manner because of the energization of the relay 16.

At this stage of the cycle, the air valve 26 actuates the associated airclutch 2| to engage the crank shaft |6 with its associated moto-r, thuscausing the upper platen 4 to be urged downwardly compressing the work(not shown) which may consist of plastic material between top and bottomdies, the 'bottom die being seated on the platen 6, as will be apparentto those skilled in the art. At this point, under the pressure of thetop platen 4, the bottom platen moves downwardly forcing hydraulic fluidfrom the cylinder 28 through the supply line 40 and the holding valve 42against the resistance of the springpressed stem 48 which is adjusted bythe screw 5| to open at a predetermined pressure, for example, 300 lbs.per square inch. Thus, the plastic material to be molded is compressedto a limited extent between the associated dies which are not yetcompletely closed because of the yielding action of the bottom platen 8.At this stage of the cycle, the plastic material is thereby permitted toheat and to expel air bubbles from between the molds in what is known inthe art as the heating and breathing period of the cycle.

When the top platen 4 reaches its lowermost .or advanced position, a cam96, driven in any .convenient manner by the crank shaft |6 such as,

for example, by a chain of gears (not shown) actuates the switch 92opening the contact points 94 and 96 and closing the contact points 98and |08. rlhe opening of the contact points 98 and 96 breaks thebefore-mentioned holding circuits through the relay 16 and the air valve26, causing the platen 4 to stop inasmuch as the air valve actuates itsassociated clutch 2| to disengage the crank shaft from its associatedmotor.

The closing of contact p-oints 93 and |80 establishes a circuit throughthe conventional timer |82 which, after a predetermined length of timenecessary to complete the heating and breathing period of thecycle,closes the contact points lcd and |66'by the switch member lill, therebyestablishing circuits through the actuating solenoid |09 of the by-passvalve 58 and through the ytimer |08. This causes the by-pass valve toclose,

which permits the pump to build up a relatively high pressure, forexample, 2000 lbs. per square inch in the supply line 46, thereby movingboth stems 46 and 48 of the holding valve 42 to their open positions asthe high pres-sure fluid flows through the supply line 49 into thecylinder 28 forcing the bottom platen 6 upwardly to close the moldingdies against the upper platen 4, thereby compressing the plasticmaterial within the dies to its final form. After a predetermined periodoftime necessary to permit the plastic material to set or solidify, thetimer |88 opens contact points ||0 and ||2 by lifting the switch member||3 from engagement therewith in conventional manner, thus breaking thebefore-mentioned circuit through the by-pass solenoid |69 and therebycausing the by-pass valve 56 to open, whereupon pressure in the supplyline 48 drops to the holding valve setting determined by the adjustablescrew 5| and registered by the gauge H4.

The operator then pushes the starting button 14 again, closing circuitsthrough the relay 'I6 and the air valve 26, the latter being operable toagain cause rotation of the crank shaft i6 which thus moves the upperplaten ,ll to its uppermost or retracted position, whereupon the cam 98opens the contact points ||6 and ||8 by moving the switch member |28from engagement therewith. This breaks the circuits established throughthe relay 16 and the air valve 26, thereby stopping the upper platen inits uppermost or retracted position for the start of a new cycle. As theplaten 4 moves upwardly, the air pressure in the reservoir 52, which mayhave a value, for example, of approximately 90 lbs. per square inch,causes the hydraulic uid in the system to be urged through the supplyline 46 and through the holding valve 42 by moving the valve stem 49 toits open position. This permits the fluid pressure within the system tomove the bottom platen 6 to its uppermost or advanced positionpreparatory to a new cycle. The conventional timers |62 and |68, as willbe clearly understood by those skilled in the art, automatically set totheir original positions, as shown in the drawing, and the device isthus placed in condition for the start of a new cycle- A stop button |22is provided for operating a switch member |2ll, and it will beunderstood from a consideration of the drawing that by pushing the stopbutton in the event of an emergency, the press may be stopped at anypoint in its cycle inasmuch as the switch member |24 is moved out ofengagement with the contact points |26 and |28 through which all of theabove-mentioned I1' desired, the holding valve 42 may be eliminated andthe compressed air within the reservoir 52 may be built up by means of aconventional compressor to the value at which it is desired to have theplaten 6 yield under the thrust of the platen It. This arrangementwould, of course, require unusually strong stops limiting expansion ofthe unit 27 at the end of a cycle. However, it is conceivable that thisarrangement may be possible under certain conditions, and it is to beunderstood that my invention is broad enough to cover such a system.

It is to be understood that I do not wish to be limited by the exactembodiment of the device shown which is merely by way of illustrationand not limitation as various and other forms of the device will, ofcourse, be apparent to those skilled in the art Without departing fromthe spirit of the invention or the scope of the claims.

I claim:

1. In a press, opposed platens, mechanical actuating means forreciprocating one of said platens, hydraulic motor means operativelyassociated with the other paten and including a cylinder and a ramslidably tted therein, a fluid supply line connected to said cylinder,means for supplying hydraulic iiuid under pressure to said line, aholding valve in said line between said cylinder and said lastmentionedmeans, said valve being adapted to accommodate ilow or iiuidtherethrough in either direction whenever the pressure in said linereaches a predetermined value, and said valve being adapted toaccommodate iiow of fluid therethrough in the direc tion toward saidcylinder when the pressure af forded by said supplying means is greaterthan that within said cylinder and greater than a Dredeterrnined valuesubstantially lower than said mst-mentioned value, said supplying meanscomprising a hydraulic circuit including a pump having its suction sideconnected t0 a reservoir of hydraulic fluid and its discharge sideconnected to said line, and fluid passage means includingr a by-passvalve connecting said reservoir to said line at a point between saidpump and said holding valve, said reservoir including means for exertinga pressure on the fluid therewithin, said last-mentioned pressure beingsubstantially less than said first-mentioned value and greater than saidsecond-mentioned value, and electrically operated control meansoperatively associated With said actuating means for automaticallyrendering the same inoperative when said one platen reaches its advancedposition, said control means including means for automatically closingsaid by-pass valve after a predetermined interval of time subsequent tothe time at which said one platen reaches said advanced position.

2. In a press, opposed top and bottom platens, mechanical operatingmeans for advancing and retracting said. top platen toward and away fromsaid bottom platen, actuating means associated with said bottom platenfor advancing it toward said top platen, said actuating means comprisinghydraulic motor means including a cylinder and. a ram slidably fittedtherein, a hydraulic supply line connected to said cylinder, a source ofhydraulic pressure iiuid connected to said line, a holding valve in saidline between said source and said cylinder, said valve being adapted t0accommodate flow of iiuid in said line away from said cylinder when thepressure therein reaches a predetermined va'ue, and said valve beingadapted to accommodate flow of iluid in said line toward said cylinderwhen the pressure from said source is at a predetermined minimum valuesubstantially lower than said first-mentioned value, said sourcecomprising a reservoir of hydraulic iluid under pressure equal to saidsecond-mentioned value, a pump having its suction side con,- nected tosaid reservoir and its discharge side connected to said line, and aconnection between said reservoir and said line at a point intermediatesaid pump and said valve, said connection comprising a by-pass valve,and control means operatively associated with said operating means andsaid by-pass valve for automatically stopping said operating means whensaid top platen reaches its advanced position and for closing saidby-pass valve at a predetermined time intervalA after said top platenreaches said advanced position.

3. In a press, opposed platens, operating means for advancing andretracting one of said platens toward and away from the other, hydraulicmotor means operatively associated with said other platen and includinga cylinder and a ram slidably fitted therein, a hydraulic supply lineconnected to said cylinder, a hydraulic pressure system connected tosaid line, a holding valve in said line lbetween said system and saidcylinder, said valve being adapted to accommodate flow of iluidtherethrough away from said cylinder when the pressure therein reaches apredetermined value, and said valve being adapted to accommodate iiow offluid therethrough toward said cylinder when the pressure from saidsystem is greater than that within said cylinder and greater than apredetermined value substantially less than said rst-mentioned value,said system comprising a reservoir of hydraulic iluid under pressure atleast equal to said secondmentioned value, pump means for developinghydraulic pressure substantial y greater than either of said values, andvalve means for lby-passing said pump means, and electrically operatedcontrol means operatively associated with said operating means and saidvalve means for stopping movement of said one platen after it hasreached its advanced position, said control means being operative toclose said valve means after a predetermined time interval subsequent tothe stop ping of said one platen.

4. In a press, opposed top and bottom platens, operating means forreciprocating said top platen, actuating means associated with saidbottom platen and comprising hydraulic motor means including a cylinderand a ram slidably tted therein, a hydraulic supply line connected tosaid cylinder, a source of hydraulic pressure fluid connected to saidline, a holding valve in said line between said source and saidcylinder, said valve being adapted to accommodate ilow of fluid in saidline away from said cylinder when the pressure therein reaches apredetermined value, and said valve being adapted to accommodate flow offluid in said line toward said cylinder when the pressure from saidsource is at a predetermined value substantially less than' saidrstmentioned value, said source comprising a reservoir of hydraulicfluid under pressure at least equal to said second-mentioned value, apump having its suction side connected to said reservoir `and itsdischarge side connected to said line and to said reservoir, and aconnection including a bypass valve between said line and said reservoirat a point in said line intermediate said pump and said holding valve,and electrically operated control means operatively associated with saidoperating means and said by-pass valve for automatically stopping saidoperating means when 7 said top platen reaches its advanced position,said control means being operative to close said bypass valve after apredetermined time interval subsequent to the stopping of said operatingmeans.

5. In a press, opposed platens, operating means for advancing andretracting one of said platens toward and away from the other, actuatingmeans operatively associated with said other platen and includinghydraulic motor means comprising a cylinder and a ram slidably iittedtherein, a hydraulic uid supply line connected to said cylinder, ahydraulic pressure system connected t said line, a holding valve in saidline between said system and said cylinder, said valve comprising meansfor accommodating iiow of fluid therethrough in the direction away fromsaid cylinder when the pressure therein reaches a predetermined valueresulting from the thrust oi said iirst-mentioned platen, and said valvecomprising means for accommodating now of fluid in said line toward saidcylinder when the pressure from said system exceeds the pressure withinsaid cylinder, said system comprising a reservoir of hydraulic fluidunder constant pressure and pump means for developing hydraulic pressuresubstantially greater than said value, valve means for by-passing saidpump means, and control means operatively associated with said operatingmeans and said valve means for stopping said operating means when saidone platen reaches its advanced position and for opening said Valvemeans after a predetermined time interval subsequent to the stopping ofsaid operating means;

6. In a press, opposed platens, actuating means for reciprocating one ofsaid platens, hydraulic actuating means operatively associated with theother platen and including a cylinder and a ram slidably fitted therein,a iluid supply line connected to said cylinder, means for supplyinghydraulic uid under pressure to said line, a holding valve in said linebetween said cylinder and said last-mentioned means, saidvalve beingadapted to open whenever the pressure therein reaches a predeterminedvalue, said supplying means comprising a hydraulic circuit including apump having its suction side connected to a reservoir of hydraulic fluidand its discharge side connected to said line, and a connection betweensaid reservoir and said line at a point therein intermediate said pumpand said valve, said connection comprising a by-pass valve, saidreservoir containing a charge of compressed gas exerting a pressure onthe fluid therein, and electrically operated controlmeans operativelyassociated with said first-mentioned actuating means for automaticallystopping said one platen in its advanced position, said control meansincluding means for automatically closing said by-pass valve after apredetermined interval of time subsequent to the stopping of said oneplaten'.

7. In a press, opposed platens, actuating means for reciprocating one ofsaid platens, actuating means associated with the other platen andincluding a cylinder and a ram slidably tted therein, a fluid supplyline connected to said cylinder, means for supplying hydraulic nuidunder pressure to said line, a holding valve in said line between saidcylinder and said last-mentioned means, said valve being adapted to openwhenever the pressure in Said cylinder reaches a predetermined value,said supplying means comprising a hydraulic circuit including a pumphaving its suction side connected to a reservoir of hydraulic iiuid andits discharge side connected to said line, and a connection between saidline intermediate said pump and said valve, said lastmentionedconnection comprising a by-pass valve, said reservoir containing meansfor exerting a pressure on the fluid therein, and control meansoperatively associated with said actuating means for automaticallystopping said one platen in its advanced position, said control meansincluding means for automatically closing said by-pass valve after apredetermined period of time subsequent to the stopping of said oneplaten.

8. In a press, opposed platens, actuating means for reciprocating one ofsaid platens, hydraulic motor means operatively associated with theother1 platen and comprising a cylinder and a ram slidably fittedtherein, a iiuid supply line connected to said cylinder, means forsupplying hydraulic fluid under pressure to said line, saidlast-mentioned means comprising a hydraulic circuit including a pumphaving its suction side connected to a reservoir of hydraulic fluid andits discharge side connected to said line and also to said reservoir,and a by-pass valve in said circuit between said reservoir and thedischarge side of said pump, said reservoir including means for exertinga pressure on the iiuid therewithin, said pressure being substantiallyless than the capacity of said pump, and control means operativelyassociated with said actuating means for automatically stopping saidiirst-mentioned platen in its advanced position, said control meanscomprising means for automatically closing said by-pass valve after apredetermined period of time subsequent to the stopping of saidfirst-mentioned platen.

9. In a press, opposed platens, operating means for advancing andretracting one of said platens toward and away from the other, actuatingmeans associated with said other platen and comprising hydraulic motormeans including a cylinder and a ram slidably fitted therein, ahydraulic supply line connected to said cylinder, a source of hydraulicpressure uid connected to said line, said source comprising a reservoirof hydraulic uid under pressure, pump means for developing hydraulicpressure substantially greater than said first-mentioned pressure, andvalve means for bypassing said pump means, and control means operativelyassociated with said operating means and said valve means forautomatically stopping said one platen when the latter reaches itsadvanced position and for automatically closing said by-pass valve meansafter a predetermined time interval subsequent to the stopping of saidone platen.

10. In a press, opposed platens, mechanical actuating means forreciprocating one of said platens, hydraulic motor means operativelyassociated with the other platen, a hydraulic uid supply line connectedto said motor means, a source of hydraulic pressure connected to saidline and including a pump, a holding valve` in said line be- 11. In apress, opposed platens, operating means for one of said platens,hydraulic motor means associated with the other' platen and including acylinder therein and a ram mounted on the press and slidably fittedwithin said cylinder, a hydraulic liuid supply line connected to saidcylinder, a reservoir of hydraulic fluid under predetermined pressureconnected to said line, pump means connected to said line for developinghydraulic pressure therein substantially greater than said rst-mentionedpressure, means for bypassing said pump means, and control meansoperatively associated with said operating means and said by-pass meansfor stopping said one platen when it reaches its advanced position, saidcontrol means being operative to automatically close said by-pass meansafter a predetermined time interval subsequent to the stopping of saidone platen.

12. In a press, opposed platens, operating means for one of saidplatens, hydraulic motor means for the other platen including a cylinderand a ram slidably tted therein, a hydraulic fluid supply line connectedto said cylinder, a reservoir of hydraulic iiuid under predeterminedpressure connected to said line, pump means connected to said line fordeveloping hydraulic pressure therein substantially greater than saidrstmentioned pressure, means for by-passing said pump means, andelectrically operated control means operatively associated with saidoperating means and said by-pass means for stopping said one platen whenit reaches its advanced position, said control means being operative toautomatically close said by-pass means after a predetermined timeinterval subsequent to the stopping of said one platen.

13. In a press, opposed platens, actuating means for reciprocating oneof said platens, hydraulic motor means operatively associated with theother platen, a hydraulic fluid supply line connected to said motormeans, a source of hydrauLc pressure connected to said line, a holdingvalve in said line between said source and said motor means, said valvevbeing adapted to open when the pressure in said line reaches apredetermined value, said source including a pump, by-pass valve meansconnected to said pump, and control means for automatically stoppingsaid one platen in its advanced position, said control means includingmeans for automatically closing said by-pass valve means after apredetermined time interval subsequent to the stopping of said oneplaten.

14. In a device of the class described, opposed platens, actuating meansfor one of said platens, a hydraulic motor operatively associated withthe other platen, a hydraulic circuit connected to said motor foractuation thereof, said circuit including a pump having its dischargeside connected to said motor, and valve means for by-passing thedischarge of said pump from said motor, and control means forautomatically rendering said actuating means inoperative when said oneplaten reaches its advanced position, said control means comprisingmeans for closing said by-pass valve means after said actuating meanshas been rendered inoperative, said hydraulic circuit com prising valvemeans between said motor and said pump for resisting flow of fluid fromsaid motor until a predetermined pressure has been built up therein bythe thrust of said one platen as the latter advances toward said otherplaten.

15. In a device of the class described, opposed platens, actuating meansfor one of said platens,

1.0 a hydraulic motor operatively associated with the other platen, ahydraulic circuit connected to said motor for actuation thereof. saidcircuit including a pump having its discharge side connected to saidmotor, and valve means for by-passlng the lo. ln a hydraulic press,opposed platens, acme` ating means for reciprocating one or' theplatens,

hydraulic motor means operatively associated with the other platen, ahydraulic circuit operatively connected to said motor means, saidcircuit comprising a line including holding valve means restricting flowof fluid from said motor means until a predetermined pressure has beenbuilt up therein, a reservoir of fluid under pressure, a pump having itssuction side connected to said reservoir and having its discharge sideconnected to said line, a connection between said discharge side andsaid reservoir including a by-pass valve,

and automatic means orstopping said one platen V in its advancedposition and for closing said bypass valve at a predetermined period oftime subsequent to the stopping of said one platen.

l'l. In a device of the class described, opposed platens, operatingmeans for one of said platens, actuating means for the other platenincluding cylinder means and ram means reciprocal therein, a hydrauliccircuit comprising a supply line connected to said cylinder means, anaccumulator connected to said line and containing a body of hydraulicfluid under relatively low pressure, a source of relatively highpressure, and control means for automatically stopping said one platenin an advanced position thereof, said control means comprising means forautomatically closing the connection of said accumulator to said lineand for simultaneously directing pressure from said lsource into saidline at a predetermined time subsequent to the stopping of said oneplaten.

18. In a device of the class described, opposed platens, actuating meansfor one of said platens, hydraulic motor means for the other platenincluding cylinder means and ram means reciprocal therein, a hydrauliccircuit connected to said cylinder means, said circuit including asupply line, an accumulator connected to said line and containing a bodyof hydraulic uid under relatively low pressure, a pump having itsdischarge side connected to said line and having its suction sideconnected to said accumulator, a by-pass valve in the connection betweensaid accumulator and said iine, and control means for automaticallystopping said one platen in an advanced position thereof, said controlmeans being operable to automatically close said by-pass valve after apredetermined time interval subsequent to the stopping of said oneplaten.

19. In a device of the class described, opposed platens, hydraulic motormeans associated with one of said platens including cylinder means andram means reciprocal therein, a hydraulic circuit comprising a supplyline connected to said cylinder means, an accumulator containing a bodyof pressure duid connected to said line, by-pass valve means in saidlast-mentioned connection, a pump having its discharge and suction sidesconnected to said line and said accumulator respectively, operatingmeans operatively associated with the other platen, and control meansfor automatically rendering said operating means inoperative When saidother platen reaches an advanced position thereof, said control meansbeing operable to close said by-pass valve means at a predetermined timesubsequent to the stopping of said other platen.

20. In a device of the class described, opposed platens, hydraulic motormeans associated with one of said platens including cylinder means andram means reciprocal therein, a hydraulic circuit comprising a supplyline connected to said cylin der meansranmaccumulator containing abody-of pressure uid connected to said line, by-pass valve means in saidlast-mentioned connection, a pump having its discharge and suction sidesconnected `to said line and rsaid accumulator respectively,

operating means operatively associated with the other platen, controlmeans for automatically rendering said Aoperating means inoperative whensaid other platen reaches an advanced position thereof, said controlmeans being operable to clo-se said by-pass valve means at apredetermined time subsequent to the stopping of said other REFERENCESCITED The following references are of record in the file of this patent:

YUNITED STATES ATENTS Name Date l MacMillin Aug. 23, 1938 Stacy May 30,`1944 Stacy June 24, 1930 Brown, Jr Feb. 22, 1927 Number

